This invention relates to battery containers the walls of which include resilient ribs integrally molded therewith and which project at acute angles into the cell compartment(s) to firmly engage and retain the battery's electrochemical innards in the container regardless of the thickness of the innards.
Automobile lead-acid storage batteries have standardized outside dimensions in different size categories. Battery manufacturers typically provide batteries with varying energy capacities in each size catagory. This is done by varying the number of positive and negative plates in each cell element which comprises the battery's electrochemical innards. Varying the number of plates in turn varies the thickness of the cell element that must be positioned and firmly retained in the containers' cell compartment(s). Traditionally, the lower energy batteries contain about nine plates per cell element while the higher energy batteries can contain as high as sixteen plates per element and these elements vary in thickness from about 2.42 cm to about 4.24 cm, respectively. Each cell element is spaced from the walls of the cell compartment and firmly held substantially centrally therein by ribs integrally molded normal to the walls defining the compartment. Larger ribs (i.e., in greater relief from the wall) are used for the thin cell element and conversely smaller ribs for the thicker cell elements.
To provide a variety of battery models, many battery manufacturers have had to inventory at least one case mold for each battery model it sells and has had to shut down its production line to change over from one model to the next. Other manufacturers inventory a lesser number of molds and incorporate inert spacers (e.g., extra separators) in each cell element to add thickness to cell elements having a fewer number of plates. This approach, however, adds the extra cost of the spacer and frequently complicates the in-plant handling of the cell element particularly during its insertion into the container.
At least one manufacturer molds oversized ribs in a few standardized containers and then cuts the ribs back to the desired size depending on the thickness of the cell element destined for the particular container. This technique is disclosed in U.S. Pat. Thune 4,041,603 issued Aug. 16, 1977 and assigned to the assignee of the present invention. This approach requires a separate trimming operation and tools therefor.
Still other manufacturers have proposed molding resilient ribs at angles to the container walls which ribs deflect by an amount commensurate with the thickness of the cell element inserted in the cell compartment. The resilient ribs are said to improve the vibration resistance of the batteries having the thicker cell elements. Containers having resilient ribs angling from the walls offer considerable resistance to the insertion of the cell elements during the "casing out" step of the assembly operation. Moreover, forcing the elements into the cell container against the action of the ribs often causes the ribs to tear separators enveloping the end plates or otherwise deleteriously affect the cell element. Resistance to insertion becomes even more acute as the cell element approaches the bottom of the cell container where the base of the rib is attached to the bottom of the container. With the base of the rib attached to the bottom of the container, the lower, or element retaining, portion of the rib is less free to flex than portions of the rib more remote from the base hence creating greater insertion resistance as the cell element is inserted deeper and deeper into the container during "case-out".
It is an object of the present invention to provide a battery container having integrally molded resilient ribs for retaining the battery's electrochemical innards which ribs are so shaped as to facilitate insertion of the cell innards into the container without deleteriously affecting the innards. It is a further object of the present invention to provide a process and means for reshaping as-molded, angling, resilient battery-container ribs to provide ribs having less resistance to cell element insertion and less tendency to damage a cell element during insertion. It is a still further object of the present invention to provide a process and means for reshaping as-molded resilient battery container ribs and to concurrently tear the base of the rib away from the bottom of the container.